Data access is the part of our service that helps us to perform reading or writing operations on the data source. The data access section is usually combined with an ORM. In general, we can define an ORM as an object-relational mapping tool for converting relational data between incompatible type systems using an object-oriented programming approach. 

ORM tools or packages are a bridge between a data source and a web application. They map the information represented in relational tables into classes and, consequently, objects.

In the .NET ecosystem, we can choose between a vast number of different ORMs. The one that is officially maintained by Microsoft is EF Core.

EF Core is an open source ORM powered by Microsoft and the community. It is the default ORM used in .NET Core applications and web services. In this chapter, we will also have an overview of Dapper, an open source micro-ORM powered by Stack Exchange and the community. Both EF Core and Dapper are distributed as NuGet packages, and, in general, they are very well integrated with the .NET Core framework.